Design and experimental validation of a low-profile wideband metamaterial absorber by characteristic modes analysis

Abstract A wideband microwave metamaterial absorber (MMA) with a relative absorption bandwidth of 127.3% and the actual thickness of only 0.084λL at the lowest operating frequency is presented in this paper. Compared with other MMAs, the characteristic modes theory is proposed to guide our design and shows an excellent performance with wider bandwidth, lower profile, and fewer modes. Characteristic modes analysis (CMA) shows a wideband modal significance (MS) over 0.707 (MS > 0.707) by exciting one mode from 1.38 GHz to 6.44 GHz, suggesting that the MMA achieves a wideband absorption performance by exciting only one mode. According to the surface current distributions, the natural modes’ current under the normal direction has the same direction with modal current shows that the mode has been successfully excited. The input impedance also illustrates a wideband match characteristic with free space. A prototype has been designed, fabricated, and measured. Measurements and simulation results show a wideband absorption with a high absorption rate of over 90% range from 1.44 to 6.32 GHz. Our design demonstrates that CMA is an effective method to design absorbers.